In robotic surgery virtual boundaries are created using computer aided design software to delineate areas in which an end effector of a robotic system can maneuver from areas in which the end effector is restricted. For instance, in orthopedic surgery a virtual cutting boundary may be created to delineate sections of bone to be removed by the end effector during the surgery from sections of bone that are to remain after the surgery.
A navigation system tracks movement of the end effector with respect to the virtual cutting boundary to determine a position and/or orientation of the end effector relative to the virtual cutting boundary. The robotic system cooperates with the navigation system to guide movement of the end effector so that the end effector does not move beyond the virtual cutting boundary.
Typically, virtual cutting boundaries are created prior to surgery. Virtual cutting boundaries are often created in a model of a patient's bone and fixed with respect to the bone so that when the model is loaded into the navigation system, the navigation system can track movement of the virtual cutting boundary by tracking movement of the bone.
Virtual boundaries may define other anatomical features to be avoided by the end effector during surgery. Such features include nerves or other types of tissue to be protected from contact with the end effector. Virtual boundaries are also used to provide virtual pathways that direct the end effector toward the anatomy being treated. These examples of virtual boundaries are often fixed in relationship to the anatomy being treated so that all of the boundaries are tracked together as the anatomy moves. However, some anatomical features or other objects in the operating room may move relative to the anatomy being treated. For instance, retractors used to provide an opening in tissue for the end effector may move relative to the anatomy being treated. If not accurately tracked using an appropriate dynamic virtual constraint boundary, the end effector may inadvertently strike the retractors. As a result, the end effector may be damaged or become inoperative and the retractor may become dislodged from its position.
Other typically untracked objects may also be in proximity to the end effector that should be avoided by the end effector, yet move relative to the anatomy being treated. Therefore, there is a need in the art for systems and methods for creating dynamic virtual boundaries for such objects.